|Illinois ranks fifth among the most populous states of the US with an estimated population of about 12,901,563 residents in 2008. It is spread in an area of 57,918 square miles, which makes it the 25th largest state in the United States of America by size. It is bordered by Indiana to the east, Wisconsin to the north, Missouri to the west and Kentucky to the south. The Mississippi river separates it from the state of Missouri whereas the Ohio river forms a borderline with Kentucky. Lake Michigan situated at the northeastern border separates it from the state of Michigan. The highest point in the Illinois is Charles Mound with a height of 1,235 feet and the lowest is Mississippi river with a depth of 279 feet. The state is marked by demographically diverse population and presence of a broad economic base, which makes it a miniature model of the US. Natural resources, such as timber, coal and petroleum are found in abundance, which gave rise to a number of small industrial cities here. Illinois attained its statehood in 1818 and was included in the Union as the 21st state. Population is concentrated mainly in the northeastern corner, in and around the city of Chicago, the capital of the state.